Work through these common causes in order.

1. Check the password — a recently changed password (article 80) must be updated in your mail app.
2. Check the mailbox isn't full — if it's over quota, raise it (article 81) or delete old mail.
3. Verify your server settings — confirm the IMAP/SMTP servers and ports (article 75).
4. Test in webmail — if webmail works (article 69), the problem is in your device's settings, not the mailbox.
5. Check DNS/MX records — incoming mail needs correct MX records (article 134).
6. Outgoing blocked? — make sure SMTP authentication is enabled and you're using port 465 or 587.

Note: If webmail sends and receives fine but your phone or Outlook doesn't, the issue is the app's settings — recheck them against article 75. If webmail also fails, contact support@hostingpartners.co.za.